The present invention relates to an optical multiplexer/demultiplexer for use in optical communications and optical measuring.
In a ferrule used in an optical multiplexer/demultiplexer, a capillary for fixing an optical fiber is formed of glass or zirconia.
A glass capillary is produced by drawing heated glass and cutting it. A wire is put through a fiber hole of the capillary, then an abrasive is fed there to polish inside and the outside of the capillary is ground to yield a predetermined standardized product. A zirconia capillary after sintering is pressed into a part, thereby yielding a ferrule. To provide a predetermined standardized product, the zirconia capillary is subjected to the same treatments as the glass capillary undergoes.
Because an optical multiplexer/demultiplexer according to the related art has a capillary produced in the above-described manner, the processing takes time and labors, making the ferrule expensive, disadvantageously.
Because the fiber hole of the capillary is polished, when there are plural fiber holes, it is hard to achieve parallelism between the fiber holes. In an optical multiplexer/demultiplexer assembled with a ferrule using such a capillary, the directions of beams incident to light incident fibers or the directions of beams outputting from light output fibers differ from one another. This leads to a large coupling loss to other optical components.
A capillary may be used in an optical multiplexer/demultiplexer in which a plurality of fiber holes, e.g., two fiber holes, laid side by side with the pitch between the fiber holes set to the diameter of an optical fiber and lights outputting from both optical fibers are incident to an optical filter via a lens.
In such an optical multiplexer/demultiplexer, the optical axes of the two optical fibers are shifted from the center of the capillary and thus from the optical axis of the lens, the incident angle of the beam that enters the optical filter through the lens becomes large, thus increasing a PDL (Polarization Dependent Loss). When the focal length of the lens is 1.8 mm, for example, the angle of incidence to the optical filter becomes 4 degrees.
Such an undesirable increase in PDL occurs even in case of a single optical fiber when the optical axis of the optical fiber is shifted from the optical axis of the lens so that the incident angle of a beam incident to the optical filter becomes larger.
Another problem arises when the fiber holes are laid out close to one another. At the time the capillary undergoes a treatment, such as polishing, the walls of the adjoining fiber holes may be broken and linked together.
Accordingly, it is an object of the present invention to provide an optical multiplexer/demultiplexer which allows a fiber hole to be formed with a high precision and can suppress a PDL to a low level.
To achieve the above object, according to the present invention, there is provided an optical multiplexer/demultiplexer wherein an optical fiber, attached to a ferrule, for receiving and outputting light, a lens member and an optical component are optically coupled, the ferrule being formed of a synthetic resin and having at least one fiber hole formed therein.
The above object and other objects, the features and advantages of the present invention will become more apparent from the detailed description given hereinafter in conjunction with the accompanying drawings.